The two-time Oscar winner and prominent Hollywood liberal was forced to apologise publicly for taking part following criticism from human rights groups. Swank said she was unaware of the allegations against her host.

The first casualty of the affair was Swank's manager, Jason Weinberg, who was fired last week. It was Weinberg, whom Swank thanked in her best actress Oscar acceptance speech for Million Dollar Baby in 2005, who apparently made the decision to email the New York-based Human Rights Foundation, which had expressed concern over Swank's involvement with Kadyrov.

Weinberg claimed the actor had "no current plans to attend" the party; later the same month, YouTube footage showed Swank eulogising her host. "I could feel the spirit of the people, and I could see that everyone was so happy," she said in the capital, Grozny. "Happy birthday, Mr President!"

Following her apology, Swank also promised to distribute her attendance fee to "various charitable organisations". A source told the Independent on Sunday: "Hilary values her liberal credentials and is close to Michelle Obama. She's really upset by what happened. It's partly her fault. But what can she do? She can hardly fire herself."

Swank is also severing ties with staff at Creative Artists Agency (CAA), including talent managers Amie Yavor and Josh Lieberman, who reportedly made the Chechen booking. Her partner of five years, John Campisi, is a CAA employee, but Swank is not leaving the company, which is one of Hollywood's most powerful agencies.

Swank was not the only well-known figure to attend the multimillion-pound Grozny ceremony on Kadyrov's birthday, which was held on a floating platform on the river Sunzha earlier this month. Action star Jean-Claude Van Damme, British violinist Vanessa-Mae and singer Seal were also reportedly paid six-figure sums to attend.

They have refused to apologise or return their fees, and Seal has even hit back at critics via Twitter. "You sit there under the umbrella of democracy and never once stop to think how it keeps you dry," he wrote.